Mucins have several important functions in the oral cavity such as soft and hard tissue coating and lubrication as well as the modulation of the oral microflora. Rat submandibular gland mucin (RSMG mucin) is a 114 kDa molecular weight glycoprotein made up of a protein core and carbohydrate side chains that are O-glycosidically linked to serine and threonine residues. A protein's glycosylation pattern is neither random nor uncontrolled, and it reflects the functional properties of the glycoprotein. The conformation, sequence, and sequence context of the protein backbone may play roles in directing glycosylation. The purpose of this study is to elucidate the in vivo glycosylation pattern of RSMG mucin and the relationship of this pattern to potential glycosylation sites. RSMG mucin has been purified from gland homogenate by anion exchange and gel filtration chromatography. Glycosylation protects the protein backbone from enzymatic degradation so the mucin was subjected to enzymatic cleavage by pronase. The purified glycopeptides obtained from the digest will be subjected to amino acid sequence analysis which should provide information regarding the occupancy of potential O-glycosylation sites. A better understanding of the signals directing glycosylation will allow their manipulation, and in turn altering mucin properties.